1. Field of the Invention
The present invention relates generally to artificial body members, and more specifically, pertains to a pivoting disc heart valve having a non-circular valve body.
2. Description of the Prior Art
Diseased or damaged heart valves are now surgically replaced with artificial heart valves. With certain artificial valves, attempts have been made to duplicate the action of natural valves. At least one such valve has employed actual human tissue (fascia lata) in a graft technique as set forth by Cooley et al in U.S. Pat. No. 3,739,402. Mechanical heart valves, that is, valves employing rigid occluders moveable physically or pivotally or both between occluding and nonoccluding positions, are generally preferred by surgeons and have largely replaced other artificial valves. The use of pre-manufactured mechanical heart valves shortens the time required for surgery since there is no need for the surgeon to fashion a valve from human tissue to the correct size and shape during surgery. Moreover, the use of mechanical valves avoids sterility problems since the valves can be pre-sterilized. Also, no coincident or prior surgery is necessary to obtain graft tissue from the patient such as fascia lata. Finally, mechanical valves are pretested for operability, and are furnished in a variety of sizes so that the correct valve is immediately available to the surgeon for implantation during valve replacement surgery.
Mechanical heart valves ordinarily are provided with a circular valve body about which is affixed a circular sewing, or suture, ring. The natural heart orifice is first prepared for reception of the mechanical valve by surgical removal of diseased or damaged heart valve tissue and adjacent tissue that may interfere with the proper operation of the mechanical valve. During implantation, the suture ring is sewn to the natural heart tissue orifice to achieve fixation of the mechanical valve.
The circular peripheral configuration of prior mechanical heart valves is an extrapolation for using valve occluders having circular cross-sections in planes normal to the direction of blood flow. For example, the heart valve commonly known as the Smeloff-Cutter valve employs a spherical occluder in a wire basket or cage. Other valves have employed toroidal occluders, and one such valve is illustrated in U.S. Pat. No. 3,438,394. Other valves, such as the Cooley-Cutter valve, have employed disc occluders of circular cross-section. One such valve is illustrated in U.S. Pat. No. 3,725,961. Other valves, exemplified by the Lillihei-Kaster valve, have employed circular disc occluders pivotable between open and closed positions within an annular valve body. One such valve is illustrated in U.S. Pat. No. 4,021,863.
Although the orifices of the aortic and pulmonary valves in the human heart are predominently circular, the orifices of the mitral and tricuspid valves are rather elongated or oval in shape. The circular peripheries of the above-described mechanical heart valves generally match the predominently circular orifices of the aortic and pulmonary natural heart valves. As a result, the peripheral tissues of aortic and pulmonary valves are not unduly distorted when mechanical valves with circular peripheries are implanted therein. However, the implantation of a mechanical heart valve having a circular periphery into the oval shaped orifice of a mitral or tricuspid valve requires the natural orifice tissues to become distorted into a circular configuration thereby not only causing stress of the tissue comprising the natural valve orifice but also on the sutures or stitches that are employed to hold the mechanical valve in place. The permanent distortion of the peripheral natural valve orifice tissue from the normal oval configuration to the forced circular configuration does not produce any beneficial effect and the stresses produced by such distortion are best avoided.
The heart valve of the present invention is particularly characterized in having an oval exterior valve body periphery which closely conforms to the oval configuration of the natural heart valve orifice.